Die casting



Nov. 14,1933. y C. PAjcK 1,935,059

i DIE CASTINGv [Tijl Fil'eaJan. 2,' 1931 zsheets-sheT-t 1 ze f i@ lW/ Nv.14,1933. c; PACK' 1,935,059

DIE CASTING Filed Jan. 2. 1931 2 sheets-sheet 2 INVENTOR v l l I ,Charles ck es n . ATTORNEYS Patented Nov. 14, 1933 UNITED sTAT'Es PATENT OFFICE DIE CASTING Charles Pack, Jackson Heights, N. Y.

Application January 2, 1931. Serial No. 506,042

21 claims.

This invention relates to die casting and more particularly to a method and means for die casting any metal under any desired high pressure. In my copending applications Ser. No. 417,849,

illed January 2, 1930, and Ser. No. 470,859, filed July 26, 1930, I have disclosed ,and claimed a novel method and machine for die casting, in 'accordance with which disclosure a die is provided, in addition to the mold impression, with a cup, receptacle, or sleeve for receiving molten metal. This receptacle is filled manually with molten metal from a separately heated crucible, after which the die is closed and a plunger sub-,-

vstantially smaller in diameter than the recep'V tacle is forced into the receptacle, preferably upwardly, thereby displacing the center portion only of the metal into the mold. The plunger is then retracted, the die opened, and the solidied casting and the cup shaped residue are-ejected as a unit, after which the residuemay be broken from the'casting and re-melted. The aforesaid practice makes it possible to cast any metal, even those of high melting point, at high pressures, and obviates the'difiiculties of close tolerances, because the machine remains at a low temperature-and chilling of metal around the cup is provided for, thereby avoiding abrasion and wear on the plunger. The metal, being molten in a refractory crucible, remains pure and uncontami- I nated by solution of machine parts, and permits the metal or alloy being cast to be changed at 'I'he object of the present invention is to generally improve the method and machines of my aforesaid` copending applications, briey outlined above.

One important object of the present invention is to reduce the quantity of metal which must be re-.melted, by greatly reducing the quan- 40 tity of residue or solidified metal in the receptacle .'at the end of the casting operation. With this 'object in view I have found that the initially solidified metal at the top of the plunger may be used as a sealing ring or ram which moves upwardly with the plunger and prevents the escape 'of molten metal through the clearance between the plunger and receptacle. The advantages of the earlier method are retained and surpassed because the plunger is substantially smaller in diameter than the sleeve and may be provided with an open ended clearance so that'it does not have a sliding flt with any other machine part. Also. theplunger need not be retracted from out ofv a cup shaped gate or residue because only a ilat or pancake shaped residue remains. The op- (Cl. Z-6 8) eration of the machine is contrary to what might be anticipated, because although substantial clearance is employed and exceedingly high casting pressures are used, no metal escapes through the said clearance, even though the molten metal being forced into the mold forms an exceedingly sharp impression, and indeed it is dificult to prevent the formation of thin fins at the various parting surfaces, cores, and pins of the die structure. This paradoxical result is made possible by permitting the metal poured in the receptacle to 'sufficiently cool beforeforcing the plunger upwardly to form a sealing ring of solid metal between the plunger and receptacle, which sealing ring moves upwardly with the plunger and pre- A vents escape of molten metal. The permissive, cooling is determined by proper inter-relationship of various factors including the time delay after pouring the molten metal in the receptacle before operating the plunger, the temperature of the v metal when poured, and the rate of heat transfer through the plunger and receptacle, which may be varied by resorting to artificial cooling or articial heat insulation.' y A An important defect of ordinary die castings is the almost certainprevalence therein of concealed defects in the form of blow holes, fissures, and the like, The wide prevalence of such defects has been disclosed in recent years because of an attempt to ascertain the `tensile strength I or gate into the relatively large space or mold in the die, resulting in premature partial solidiilcation of the metal rst entering the mold, and, second, the shrinkageof the metal on cooling takes place in the casting and is not transferred to the gate or to the source of metal.

Accordingly, another primary object of the present invention is to make possible the manufacture of truly sound or solid die castings. This I have found may readily be accomplished by the practice of my die casting method, provided that the method and receptacle are interconnected by a preferably single gate of large cross sectional area. In the present apparatus the molten metall flows from a receptacle of large cross sectional `area through a gate of smaller but nevertheless appropriate mold impression 20,

.feige cross sectional area, and nnally into the incid impressions. The arrangement is such that the metal is forced in a continuous solid stream with no squirting or constriction of iiow. In this manner I have cast test bars Whidh are absolutely solid and which show no blow holes or hidden defects, regardless of the number of bars tested.

It has already been explained that the solidification of metal on top of the plunger and around the walls of the receptacle or sleeve provides a desirable sealing medium, and that the solidified metal at the top of the plunger rises up with the same. 'Ihis tends also to raise the solidified metal around the wall of the sleeve, and I have found that this metal may be pushed intothe gate and thereby obstruct that free oW of metal into the mold which is essential for the production of truly sound castings. Accordingly, still another object of the present invention is to check this tendency, and accordingly the upper portion of the die which closes the top of the receptacle is provided with means for preventing upward movement of the solidified metal about the wall of the sleeve. In simplest form this means may comprise merely a portion of the parting surface of the die, and it is simply necessary to make the cavity 'in the upper die which leads into the gate smaller in area than the top oi the receptacle. When the plunger ascends, the upper edge of the solidified wall metal bears against the parting surface oi' the die and is held thereby, further movement oi' the plunger being permitted by collapse or corrugation of the solidified wall metal.

Further objects of the present invention are to make it possible to dispense with the three step plunger movement described in my copending application Ser. No. 470,859; to facilitate the operation of pouring the molten metal into the receptacle, and to facilitate the operation of changing the die being used in the die casting machine. To the accomplishment of the foregoing and such other objects as will hereinafter appear, my invention consists in the die casting method and machine elements and their relation one to the other, as hereinafter are more particularly described in the specification and sought to be defined in the claims. The specification is accompanied by drawings in which:

Fig. 1 is av horizontal section taken in plan bietween the separated lower and upper die porons;

Fig. 2 is a vertical section taken in the plane of the line 2--2 in Fig. 1;

Fig.V 3 is a vertical section taken through the receptacle after metal has been poured therein and the. die closed;

Fig. 4 is a similar section showing'the plunger partially elevated;

Fig. 5 is a similar section at the end ofthe stroke of the plunger;

Fig. 6 is a vertical section similar to that shown in gig. 2, taken through a modied. form of die: an l Fig. is an inverted p view or the upper or ejector die. v.

Referring to the drawings, and more particuiarly to Figs. 1 and s, the sie casting 'mamma only a fragment of which isshown, is generally similar to that disclosed in my copending application Ser. No. 470,859. The machine includes separable die portions, speciiically a cover die 12 and an ejector die 14, and a receptacle 16 in flow communication through a gate 18 with any A pier 32 is arranged for upward reciprocation in receptacle 16 in order to force metal therefrom into the mold impression 20. In operation, the die portions are separated, preferably by elevating the ejector die 14; a quantity of molten -metal is poured into the receptacle 16; the die is then closed, after which plunger 22 is elevated to force molten metal into the mold impression 20; the plunger 22 is retracted and ejector die 14 elevated, the latter taking with it the solidified casting and residue of metal from the receptacle 16; the solidified casting and metal residue are ejected from the ejector die 14 as a unit; and, finally, the gate and residue may be broken from the casting and re-melted for further use.

As was explained in my copending applications aforesaid, to prevent wear and abrasion of a closelly iitting plunger and cylinder, the plunger may be made substantially smaller in diameter than that of the cylinder, thereby displacing only the center portion of the metal from the receptacle and permitting the balance of the metal to solidiiy about the walls of the receptacle so that the final residue is in the form of a cup. In accordance with the present invention, the freedom from wear of the plunger is increased, and at the same time the walls of the cup shaped residue are dispensed with, leaving only the top or at pancake shaped portion of the residue, thereby greatly decreasing the quantity of metal which must be re-melted after each casting operation.

The theory on which the present invention operates may best be described in connection with Figs. 3, 4, and 5 of the drawings, referring to which it should iirst be observed that the eiective portion of plunger 22 is relatively short and may be mounted upon a hydraulic piston rod 24 or like element which is smaller in diameter than the plunger 22. The plunger is itself substantially smaller in'diameter than the receptacle or sleeve 16, providing a clearance therebetween which is free and open ended. In fact the fixed plate 26 of the die casting machine, in which the sleeve 16 is mounted, is preferably cut away at 28 below the sleeve so that the plunger 22 is en- 'tirelyiree from the balance o' the machine instead of having a close sliding fit. When molten metal is poured into the receptacle 16, it at first tends to fiow between the plunger 22 and receptacle 16, but quickly solidifies and forms Aa very short and blunt fln, bead, Vor protuberance 30. This acts as a sealing ring and prevents further escape of metal.

The ejector die 14 is closed against the cover die 12 and the top edge of the sleeve 16 before the plunger 22 is elevated, and, in accordance with the present invention, Vthe operation oi the machine is so timed that a desirable amount of cooling and solidiiication of the metal in the receptacle is permitted, this solidied metal being indicated by the cross sectioned layer 32 on top of the plunger 22, and the cross sectioned layer 34 about the wall of the sleeve 16. The plunger 22 is then elevated, and the solidified metal 30 and Manises with the plunger 22, as is best shown in Fig. 2, and itself acts as a ram for ejecting metal from the receptacle 16 into the die. The wall metal 34 collapses or crumbles up and does not hinder the elevation of plunger 22. In spite of loi) in fact penetrates even the slightest undesired crevice between parting faces of the die and 'around ejector and core pins and the like, forming fins of unbelievable thinness and fragility.

f' This paradoxical contrast between the penetration of metal in the mold and the retention of metal in the receptacle is due entirely to the operation of the initially solidified metal in the receptacle as a sealing ring.

The amount of solidification needed for successful operation has been exaggerated in Figs. 3 and 4for the sake of clarity. Actually, the timing of the operation of the machine is determined empirically and depends upon numerous factors such as the particular alloy or metal being cast, the temperature of the metal when poured, and the rate of heat transfer through the plunger 22 andreceptacle 16. The choice of metal is determined by other factors, and consequently the variable factors are time, temperature, and heat transfer rate. The last named factor may be greatly increased, for example, by the use of water cooling, as by means of the water cooling ring 40, or/and water cooling passages (not shown) through piston rod 24 and plunger 22, and, on

the other hand, may be greatly decreased by spraying the interior surface of the receptacle with a spray consisting, for example, of gasoline or carbon tetrachloride or similar vehicle carrying powdered magnesium oxide or talcum or similar non-metallic powder. The resulting film re- 4 duces the heat transfer through the walls of the receptacle and thereby reduces the solidification Y of metal therein. Such a spraying operation isA not at all diicult and at present is frequently done with oil in ordinary die casting in order to put a film of oil in the mold impression of the die.

It will be evident that the proper permissive u cooling in the receptacleis determined by proper inter-relation of all of the factors outlined above. In general, variation of time is most simple.

'Howeven in special cases the time may -be itself determined by extraordinary conditions, as, for example, the long time needed to close a particularly large and complex die. In such cases variation of the other factors may be resorted to.

The plunger 22 continues its upward stroke until the'mold is lled with metal at the desired pressure, and if a properly proportioned quantity of metal has been initially poured into the receptacle, only a relatively thin, flat, more or less pancake shaped residue 38 will remain in the receptacle. as i's clearly indicated in Pig. 5. The plunger 22` is then retracted, the ejector die 14 elevated, taking with it the solidined casting and residue 38, after which the casting and residue may be ejected as a unit by appropriate ejector pins 42. i i n To facilitate retraction of the plunger 22', it is preferably slightly tapered upwardly. To facilitate withdrawal of the residue .38 from the receptacle 16, the latter is preferably slightly'tapered downwardly. These tapers are clearly but exaggeratedly shown in the drawings. 'Ihey are not essential for successful operation o f the machine, but the taper of receptacle 18 is desirable because the heat of the molten metal may alone serve to mar or check the smooth surface o f the wall of the receptacle, thereby making minute undercuts in which molten metal will now, .and from which the metal will have to be sheared. The taper of the plunger 22-is quite dispensable because of the slight depth of the bead or fin 30 from which the plunger must be withdrawn.

The clearance between the plunger 22 and the receptacle 16 has also been exaggerated in the drawings lfor the sake of clarity. This clearance may, generally speaking, be of the order of ten to fifty thousandths of an inch, although it is a variable, dependent upon the various cooling factors already outlined. In a particular machine which'was successfully operated with bronze alloys, the diameter at the top of the plunger 22 was 2.500 inches,.while the diameter at the lower portion of the sleeve was 2.550 inches. To provide a taper on the plunger, the diameter at the bottom of the same was Amade 2.510 inches, while the taper of the sleeve resulted in a diameter at the top of the sleeve of 2.600 inches. The radial clearance in this set-up ranged from twenty-five tho'usandthsofv an inch at the bottom of the receptacle to fifty thousandths of an inch at the top of the receptacle. In another set-up of apparatus used particularly with zinc base alloys, a clearance of only twelve and a half to twenty-five thousandths of aninch, instead of from twenty-five to fifty thousandths of an inch was found preferable. In any case, it is important to observe that the taper of the receptacle is suiiiciently small so that the clearance at the top is of the same order of magnitude as that at the bottom and is insuiiicient to permitoverflow of molten metal around the initially solidified sealing ring at the top of the plunger. This is in sharp contrast with the arrangement in my prior machine, in which in order to permit free withdrawal of the relatively deep cup shaped residue, a large taper is esisc i sential, for such a taper would not permit the V practice of the present invention. In other words, if yonly the bottom clearance in my prior machine were reduced, when the plunger neared tle top of the receptacle the molten metal would readily escape around the sealing ring Aand flow downwardly and again ll up the clearance space with L' a cup shaped residue of metal.

Further features of the present invention center .about the obtention of truly solid die castings. In Figs; 1 and 2 the die is indicated -as intended for the production of test bars.

ing thereto, are indicated in broken lines because the mold impression therefor islocated entirely in lche ejector die. The cylindrical test ,barv 20 is visible in Fig. 1 because half of the mold ixn- 'l pression is in the cover die l2, this being clearly evident also in Fig. 2. Such test bars have been die cast in previous years in order to investigate the strength of die cast materials, but the resulting tests have been extremely disappointingv -to the industry because they served merely to disclose the practically universal prevalence of blow holes, fissures, and similar concealed defects within die castings. I believe the absence of sound castings in ordinary die casting practice is due' to the necessary useof a small nozzle between the plunger and die -which is subsequently 4foiing is afterwards broken from the gate and may show blow holes or defects at this point of. breakage. To prevent the customer from seeing such defects, the manufacturer ordinarily makes the gate quite small at this point also, and preferably obtains the desired area in'the form of a' long thin' slit. Such practice, however, merely 1.50

The fiat test bars '44 and 48, as well as the gatesA leadbe made by causing a continuous flow of metal from the source of metal through .gates of constant or diminishing areas which finally lead into the mold impression in a direct and open manner 'such that shrinkage of metal on cooling may be taken up in the gates and evenv back at the source of metal. Thus, referring to Figs. 1 and, 2, the source of metal is the receptacle 16, and the metal forced upwardly therefrom flows in a direct and unobstructed manner through a single gate 18 of large cross sectional area and thence through branch gates 48 and 50 and finally into the mold impressions 20, 44, and 46. Risers 52 are preferably provided at the ends of the mold impressions in order to save any slag or impurities, and in order tol additionally take care of cooling shrinkage. It should further be noted that the gates 48 and 50 are preferably arranged to cause the metal to iiow backwardly after initially nlling a waste end 54. With these precautions the flow of metal resembles that heretofore found desirable in ordinary foundry practice, and at the same time the extremely high pressures and fine definition of die casting are obtained. Test bars cast in this manner are uniformly sound, and breakage of a vast number of the same has in no case disclosed a blow hole or similar concealed defect.

For the casting of small articles such as ordinary machine parts and the like, the gating may desirably be arranged in the manner shown in Figs. 6 and 7. Fig. 'l is an inverted planA view of the ejector die, and shows how the metal is preferably guided through a single main gate 60 of large cross sectional area. The gate 60 is terminated by a riser 62. After the gate 60 has been completely filled, the further flow of metal is forced through the backwardly directed branch gates 64 into the mold impressions 66. Ejector pins for finally ejecting the finished castings, gate, and residue are indicated at 68. In passing, it may be observed that in Fig. 6 the water cooling ring 40 shown in Figs. 3, 4, and 5 has been replaced by a solid ring 70, and this may be done in lieu of simply cutting off the water supply when it is desired to obtain only a moderate rate of cooling.

It is essential not only to provide a gate of large cross sectional area for the free flow of metal, but also to prevent obstruction of this gate by solidified metal inV the receptacle 16. Thus, referring to Fig. 3, the solidified wall metal 34 tends to slide upwardly with the plunger 22, and this movement, if not prevented, may result in obstruction of the gate, 18 by the Wall metal 34.

Accordingly, means are provided to prevent such movement, and this means may most simply take.

the form here illustrated, in which the parting face of ejector die 14 is arranged to project within the walls of the receptacle 16, as is indicated at 80, the gate 18 meanwhile being formed entirely in the ejector die 14. In Fig. 7 the recess 82 in the ejector die which leads directly into the gate 60, is made appreciably smaller in diameter than the inside diameter of the receptacle, the latter being indicated by the broken line 16. A peripheral or annular surface is therefore provided directly above and within the top of the receptacle, which serves to eectively arrest any attempted upward movement by solidied wall metal. In Fig. 1 the same idea is illustrated by the broken line 82 representing the recem in the ejector die Lesaosa which has a diameter substantially smaller than that of the sleeve 16.

Further features of the present invention center about the structural arrangement of the receptacle or sleeve 16 and the cover die 12, and their mounting on the machine as well as their relation one to the other. Referring to lFigs. l and 2, the cover die 12 is so designed that the end '12 thereof terminates at the center line of the sleeve 16. The cover die is further provided with a semicircular recess '74 dimensioned to mate with or fit closely against the outer periphery of the sleeve 16. The sleeve 16 is itself designed to fit into the fixed plate or bed 26 of the frame of the die casting machine, and may be provided with a @ange '16 for accurately locating the sleeve within the plate 26 and for taking part of the downward pressure exerted on the sleeve by the ejector die 14. The upper portion of sleeve 16 projects from plate 26, and it is against this projecting portion of sleeve 16 that the semicircular recess 74 in cover die l2 is fitted. The top-sur faces of the cover die 12 and the sleeve 16 are flush, the latter preferably being made several thousandths of an inch higher than the former inl order to obtain a tight seal when the receptacle is closed by the ejector die 14.

This construction possesses numerous advantages, among which may be mentioned the fact that pouring of metal into the `receptacle from a ladle is facilitated because it may readily be poured over the outer or exposed edge of the receptacle, When the .die is to be changed, the cover die may readily be removed without having to lift the same up over the receptacle. A tight fit between the cover die and the receptacle mayI be obtained without subsequent difficulty in separating the two, when it is necessary to change the die. Should the fit between the die and receptacle become inaccurate, it is merely necessary to remove a slight amount of material from the end wall '72 of the die, and thereafter again re-bore the semicircular opening 74 to the desired dimension. The sleeve 16 may readily be removed and replaced by a substitute, as in the event of dierent clearances between the plunger and sleeve proving desirable because of a. change in the metal being cast.

In the machine disclosed in my copending application Ser. No. 470,859, the plunger was arranged to have a three step movement, so that the plunger might be retracted below the initial position taken when thecup is filled with metal, in order to clear the iin at the bottom of the residue when withdrawing the residue from the receptacle, It will be evident, from an, inspection of Figs. 3, 4, and 5 of the present drawings, that such a three step movement may, if desired, be readily dispensed with, for the plunger 22 is withdrawn from the bead or fin 30 when it is dropped to its normal starting position. In other words, since the metal residue is elevated, the plunger need not be additionally lowered by a third step or movement. However, it may not be amiss to observe that the three step movement is not injurious, and, in fact, serves some useful function even when die casting in accordance with the present invention. This is so because when beginning to cast a new alloy or a new casting which may have a simple and rapidly operatable die, the desirable cooling time is unknown, and consequently metal may flow past plunger 22 because of insufficient cooling. The escape of this metal is readily observed by the operator of the machine, and the timing or other cooling justed, however, the three step movement of the plunger permits the plunger to be retracted below and entirely out of the receptacle, so that solidified metal in the clearance between the plunger and receptacle falls clear of the machine or may vreadily be brushed from the plunger and does not remain permanently in place with consequent abrasion and wear of machine parts which, in.

s casting pressure and the large clearance between proper operation, do not even contact.

of solidified metal is reduced in volume to a minimum and is of such shape that it may readily be withdrawn from the receptacle. Either a two step orl three step movement of the plunger may be employed. The flow of 4metal from the receptacle into the mold is clear, unobstructed, and

direct, so that no squirting and consequent premature partial cooling in the mold takes place, while shrinkage upon cooling may be transferred to risers and the gate, and,'in fact, all the way back to the' receptacle or originalsource of metal,

thereby making it possible to manufacture truly l sound die castings.

The structural arrangement of themachine facilitates pouring the metal into the receptacle and removal of .either the die or the receptacle.

It 'will be apparent that while I have shown and described vmy invention in the preferred forms, many changes and modifications may be made in the method land structures disclosed without departing fromthe spirit of the invention defined in the following claims. I claim: j 1. In the operation of a die casting machine n comprising a receptacle for receiving a quantity of molten metal from a, reservoir, a mold in direct communication with said receptacle, and an upwardly movable plunger substantially smaller in diameter than the receptacle for displacing metal from the receptacle into the mold, the

` method which includes pouring a measured quantityof molten metal into the receptacle, causing the metal inthe receptacle to suiciently cool,

' to form a sealing ring of solid metal between the plunger and receptacle, then' forcingv the, plunger upwardly under high pressure while most ofthe metal in the receptacle is still in unsolidifled condition, and thereby forcing the sealing ring to move upwardly with the plunger and to preventjthe escape of the molten metal from thereceptacle in spite of the high casting pressure j and the large clearance between the plunger and the receptacle.

2. In `the operation of a'die casting ,machine comprising a tapered receptaclefor receiving a quantity of molten metal froml a reservoir, a mold in direct communication with said receptacle, an upwardly movable plunger substantially smaller in diameter than the receptacle for displacing metal lfrom thereceptacle into the mold, and

`means to remove the casting from the mold andv 'ther remaining metal from the receptacle in a solid state, the method which includes pouring a measured quantity of molten metal into the receptacle, causing the metal in the receptacle to suiciently cool, to form a sealing ring of solid metal between the plunger and receptacle, then forcing the plunger upwardly under high pressure while most of the metal in the' receptacle is still in unsolidied condition, and thereby forcing the sealing ring to -move upwardly with the plunger and'to prevent the escape of the molten metal from the receptacle in spite of the high the plungery and the receptacle, said desired limited cooling being ldetermined by proper interrelation of factors including the time after pouring before the plunger is operated, the temperature of the metal when poured, and the rate of heat transfer through the plunger and receptacle.

3. In the operation of a die casting machine comprising a receptacle for receiving a quantity of moltenl metal from a reservoir, a mold in direct communication with saidreceptacle, and an upwardly movable plunger substantially smaller in diameter than the receptacle for displacing metal from the receptacle into the mold, the method which includes pouring a measured quantity of molten metal into the receptacle, causing the metal in-the receptacle to suiciently cool before forcing the plunger upwardly, to form a layer of solid metal on top of the plunger, then forcing the plungerupwardly under high pressure while most of the metal in the receptacle is still in unsolidied condition, and thereby forcing the layer to, move upwardly with the plunger and to act as aram forcing the moltenv wardly into the receptacle for displacing the metal from the receptacle into the mold, said plunger having at the maximum a diameter more than twenty thousandths of an inchsmaller than the smallest diameter of the receptacle in order to obtain an open-ended clearance therebetween such that, on the one hand, if forced against a wholly'molten charge of metal the metal will readily and freely escape past the plunger, whereas on the other hand, if the molten metal initially poured in the receptacle is first caused to partially solidify to form a relatively heavy sealing ring between the plunger and receptacle, said sealing ring moves upwardly with the plunger and prevents escape of molten metal.

5. A die casting machine comprising-a receptacle formolten metal to be cast, a. mold in communication therewith, la plunger movable `upwardly intoy the receptacle for displacing the metal from thereceptacle into the mold, said'receptacle being slightly tapered downwardly, said plunger having a maximumA diameter smaller than the minimum diameter of the receptacle in order to obtain an open-ended clearance therebetween such that, on the one hand, if forced against a wholly molten charge of metal the metal willl readily and freely escape past the plunger, whereas on the other hand, if the molten metal initially poured in the receptacle first solidies to form a. sealing ringbetween the plunger and receptacle, said sealing ring moves upwardly with the plunger and prevents escape of molten metal.

6. A die casting machine comprising a receptacle for molten metal to be cast, a mold in comiss -mum diameter of the receptacle in order to obtain a clearance therebetween such that, on the one hand, if forced against a wholly molten charge of metal the metal will readily and freely escape past the plunger, whereas on the other.

hand, if the molten metal initially poured in the receptacle ilrst solidies to form a sealing ring between the plunger and receptacle, said sealing ring moves upwardly with the plunger and prevents escape of molten metal.

7. A die casting machine comprising separable die portions including a receptacle for molten metal to be cast, a mold in communication therewith, a plunger movable upwardly into the receptacle for displacing the metal from the receptacle into the mold, said receptacle being slightly tapered downwardly, said plunger having a mammum diameter smaller than the minimum diameter of the receptacle in order to obtain a clearance therebetween such that, on the one hand, if forced against a wholly molten charge of metal the metal will readily and freely escape past the plunger, whereas on the other hand, if the molten metal initially poured in the receptacle first solidifies to form a sealing ring between the plunger and receptacle, said sealing ring moves upwardly with the plunger and prevents escape of molten metal during the subsequent movement of the plunger regardless of the casting pressure employed, and means for ejecting the resulting casting and solidified residue as a unit when the die portions are separated.

8. A die casting machine comprising separable die portions including a receptacle for molten metal to be cast, a mold in communication therewith, a plunger movable upwardly into the receptacle for displacing the metal from the receptacle into the mold, said receptacle being slightly tapered downwardly, said plunger being slightly tapered upwardly and having a maximum diameter smaller than the minimum diameter ofthe receptacle in order to obtain a clearance therebetween such that, on the one hand, if forced against a wholly molten charge of metal the metal will readily and freely escape past the plunger, whereas on the other hand, if the molten metal initially poured in the receptacle rst solidifles to form a sealing ring between the plunger and receptacle, said sealing ring moves upwardly with the plunger and prevents escape of molten metal during the subsequent movementbf the plunger regardless of the casting pressure employed, and means for ejecting the resulting casting and solidified residue as a unit when the die portions are separated.

9. A die casting machine comprising a sleeve for molten metal to be cast, a mold connected to the top thereof, a plunger movable upwardly into the sleeve for displacing metal into the mold, said plunger having a diameter at its largest cross-section of twenty to one hundred thousandths of an inch smaller than the least diameter of the sleeve, the large and open-ended clearance being such that if the plunger is forced against a wholly molten charge of metal in the sleeve the metal readily` and freely escapes past the plunger and downwardly out of the receptacle.

10. A die casting hine comp i .t a sleeve masacre for moltenV metal to be cast, a mold connected to the top thereof, a plunger movable upwardly into the sleeve for displacing the metal there from into the mold, said plunger having a diameter smaller than that of the sleeve in order` to obtain a free open ended clearance therebetween such that if the plunger is forced against a wholly molten charge of metal in thesleeve the metal readily and freely escapes past the plunger and downwardly out of the receptacle, and said sleeve being tapered downwardly to facilitate withdrawal of the residue from the top of the sleeve, the taper being sufficiently small so that the clearance at the top of the sleeve is of the same order of magnitude as that at the bottom of the sleeve and insufllcient to permit overflow of molten metal around an initially solidiiled sealing ring at the top of the plunger.

ll. A die casting machine comprising a sleeve for molten metal to be cast, a mold connected to the top thereof, a plunger movable upwardly into the sleeve for displacing the metal therefrom into the mold, said plunger having a diameter smaller than that of the sleeve in order to obtain a free open ended clearance therebetween of the order of ten to nfty thousandths of an inch,.said plunger being tapered upwardly to facilitate withdrawal from the nn resulting from the clearance, and said sleeve being tapered downwardly to facilitate withdrawal of the residue from the top of the sleeve, the taper of the sleeve being sufllciently small so that the clearance at the top of the sleeve is of the same order of itude as that at the bottom of the sleeve and insumcient to permit overflow of molten metal around/the initially solidified sealing ring at the top of the plunger.

ros

12. A die casting. machine comprising sepay rable die portions including a sleeve for molten metal to be cast, a mold connected to the top thereof,v a plunger movable upwardly into the sleeve for displacing the metal therefrom into the mold, said plunger having a diameter smaller than that of the sleeve in order to obtain a free open ended clearance therebetween such that if the plunger is forced against a wholly molten charge'of metal in the sleeve the metal readily and freely escapes past the plunger and downwardly out of the receptacle, said sleeve being tapered downwardly to facilitate withdrawal of the residue from the top of the sleeve, the taper being sufficiently small so that the clearance at the top -of the sleeve is of the same order of magnitude as that at the bottom of the sleeve and insufficient to permit overiiow of molten,

metal around an initially solidified sealing ring at the top of the plunger, and means for ejecting the resulting casting and solidified residue 'as a unit when the die portions are separated.

13. A die casting machine comprising separable tate withdrawal of the residue from the'top of Ithe sleeve, the taper of the sleeve being sumclently small so that the clearance at the top of the sleeve is of the same order of magnitude as that at the bottom of the sleeve and insumcient to permit overiiow of molten metal around e the initially solidied sealing ring at the top of the plunger, and means for ejecting the resulting casting and solidified residue as a unit when the die' portions are separated.

14. A kdie casting machine comprising a plate, a receptacle in the form of a cylindrical sleeve mounted thereon and projecting therefrom, a lower die also mounted thereon and provided with an arcuate open-sided recess at one end thereof for closely fitting against the exterior wall of the projecting portion of the sleeve, a mating upper die mounted above and arranged for movement toward and from the sleeve and lower die and serving to close the top of the sleeve, a mold formed in the separable portions of said die, a gate interconnecting the mold and receptacle, and a. plunger movable into the sleeve for displacingmetal therefrom into the mold, said plunger being substantially smaller in dameter than the sleeve with a clearance therebetween too large for pressure operation on. a

wholly molten charge of metal.

15. A die casting machine comprising a lower die portion, a receptaclefor molten metal, an upper die portion mounted above and arranged for movement toward and from the lower die, molds formed in the separable portions of said die, a gate of large cross sectional area interconnecting the molds and the top of the receptacle, a plunger movable upwardly into the receptacle for displacing metal therefrom into the mold, and means for preventing upward movement of met-al initiallysolidied about the wall of. the receptacle in order to prevent thesame from clogging the gate.

16. A die casting machine comprising a i'lxed lower plate, a receptacle in the form of a cylindrical sleeve removably mounted thereon and projecting therefrom. an'inverted cover die also removably mounted thereon, said cover die being provided with an arcuate open-sided recess at one end thereof for closely fitting against the exterior wall of the projecting portion of the sleeve, an ejector die mounted above and arranged for movement toward and from the sleeve and cover die, said ejector die projecting beyond the -cover die an amount sufiicient to close the top of the sleeve, a mold formed in the separable portions of said die, a gate interconnecting the mold and receptacle, a plunger movable upwardly into the sleeve for displacing metal therefrom into the mold, and means in said ejector die for ejecting the solidified casting and residue of metal when the ejector die is elevated.

17. A die casting machine comprising a fixed.

lower plate, a receptacle in the form of acylindrical sleeve mounted thereon and partially projecting therefrom, an inverted cover die also mounted thereon, said cover die being provided with a semicircular -recess at one end thereof for closely fitting'v against the exterior wall of the projecting portion of the sleeve, -the topedge of the sleeve being slightly higher than the top or parting face of the cover die, an ejector die mounted above and arranged for movement toward and from the sleeve and cover die, lsaid ejector die projecting beyond the cover die an4 ward movementof metal initially solidified about the wall of the sleeve, and means in said ejector die for ejecting the solidied casting and residue of metal when the ejector die is elevated.

18. A die casting machine comprising a lower |`tacle in order to obtain a clearance therebetween auch that the molten metal initially poured in the receptacle solidifies to form a sealing ring at the top. of the plunger which moves upwardly with the plunger and prevents escape of molten metal, and means for preventing upward movement of metal initially solidified about the wall of the receptacle.

19. A die casting machine comprising a lower plate, a receptacle in the form of a cylindrical sleeve mounted thereon and projecting therefrom, an inverted cover die also mounted thereon, said cover die being provided with an arcuate open-sided recess at one end thereof for closely fitting against the exterior wall of the sleeve, an ejector die mounted above and arranged 'for movement toward and fromthe sleeve and cover die, said ejector die projecting beyond the cover die an :amount sufficient to close the top of the sleeve, a mold formed in the separable portions of said die, a gate vinterconnecting the mold and receptacle, a plunger movable upwardly into the sleeve for displacing metal therefrom into the mold, said plunger having a diameter smaller than that of the sleeve in order to obtain an openended clearance therebetween such that, on the one hand, if forced against a wholly molten charge of metal the metal will readily and freely escape past the plunger, whereas on the other hand, if the molten metal initially poured in the sleeve first solidifies to form a sealing ring at the top of the plunger, said sealing ring moves upwardly with the plunger and prevents escape of molten metal, and means in said ejector die for ejecting the solidified casting and residue of metal when the ejector die is elevated.

20. A die casting machine comprising a iixed lower plate, a receptacle in the form of a cylindrical sleeve mounted thereon, an inverted cover die also mounted thereon and closely fitting against the sleeve, an ejector die mounted above andarranged for movement toward and from the sleeve 'and cover die. molds formed in the separable portions of said die, a single gate of large cross sectional area formed in said ejector die for interconnecting the .molds and receptacle, a

' plunger movable upwardly into the sleeve for displacing metal therefrom into the mold, said plunger having a diameter smaller than that of the sleeve in order to obtain an open-'ended clearance therebetween such that, on the one hand. if -forced against a wholly molten charge of metal the metal will readily and freely escape past the plunger, whereas on the other hand, if the molten metal initially poured in the sleeve rst solidies to form a sealing ring on top of the plunger, said sealing ring moves upwardly withl .the plunger and prevents escape of molten metal, means in said ejector die for preventing movement of metal initially solidified about' the wall of the sleeve, and means in said ejector die for ejecting the solidified casting and residue of metal when the ejector die is elevated.

21. A die casting machine comprising a. lower plate, a receptacle in the form of a cylindrical sleeve mounted thereon and partially projecting therefrom, an inverted cover die also mounted thereon and provided with an arcuate recess at one end thereof fitting the projecting portion of the sleeve, the top edge of the sleeve being slightly higher than the top or parting face of the cover die, an ejector die mounted above and arranged for movement toward and from the sleeve and cover die and serving to close the top of the sleeve, a mold formed in the separable portions of said die, a gate of large cross sectional areaforrned l in said ejector die for interconnecting the molds and receptacle, a. plunger movable upwardly into the sleeve for displacing metal therefrom, said sleeve being slightly tapered downwardly, said plunger being slightly tapered upwardly and having a diameter smaller than that of the sleeve in order to obtain a clearance therebetween such that molten metal initially poured in the sleeve solidifles to form a sealing ring between the plunger and sleeve which moves upwardly with the plunger and prevents escape of molten metal, means in said ejectorvdie for preventing upward movement of metal initially solidified about the wall of the sleeve, and means in said ejector die for ejecting the solidified casting and residue of metal when the ejector die is elevated.

CHAS. PACK.

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